.TH std::exp,std::expf,std::expl 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::exp,std::expf,std::expl \- std::exp,std::expf,std::expl

.SH Synopsis
   Defined in header <cmath>
   float       exp ( float num );

   double      exp ( double num );                            (until C++23)

   long double exp ( long double num );
   /* floating-point-type */                                  (since C++23)
               exp ( /* floating-point-type */ num );         (constexpr since C++26)
   float       expf( float num );                     \fB(1)\fP \fB(2)\fP \fI(since C++11)\fP
                                                              (constexpr since C++26)
   long double expl( long double num );                   \fB(3)\fP \fI(since C++11)\fP
                                                              (constexpr since C++26)
   Additional overloads \fI(since C++11)\fP
   Defined in header <cmath>
   template< class Integer >                              (A) (constexpr since C++26)
   double      exp ( Integer num );

   1-3) Computes e (Euler's number, 2.7182818...) raised to the given power num.
   The library provides overloads of std::exp for all cv-unqualified floating-point
   types as the type of the parameter.
   (since C++23)

   A) Additional overloads are provided for all integer types, which are  \fI(since C++11)\fP
   treated as double.

.SH Parameters

   num - floating-point or integer value

.SH Return value

   If no errors occur, the base-e exponential of num (enum
   ) is returned.

   If a range error occurs due to overflow, +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL is
   returned.

   If a range error occurs due to underflow, the correct result (after rounding) is
   returned.

.SH Error handling

   Errors are reported as specified in math_errhandling.

   If the implementation supports IEEE floating-point arithmetic (IEC 60559),

     * If the argument is ±0, 1 is returned.
     * If the argument is -∞, +0 is returned.
     * If the argument is +∞, +∞ is returned.
     * If the argument is NaN, NaN is returned.

.SH Notes

   For IEEE-compatible type double, overflow is guaranteed if 709.8 < num, and
   underflow is guaranteed if num < -708.4.

   The additional overloads are not required to be provided exactly as (A). They only
   need to be sufficient to ensure that for their argument num of integer type,
   std::exp(num) has the same effect as std::exp(static_cast<double>(num)).

.SH Example


// Run this code

 #include <cerrno>
 #include <cfenv>
 #include <cmath>
 #include <cstring>
 #include <iomanip>
 #include <iostream>
 #include <numbers>

 // #pragma STDC FENV_ACCESS ON

 consteval double approx_e()
 {
     long double e{1.0};
     for (auto fac{1ull}, n{1llu}; n != 18; ++n, fac *= n)
         e += 1.0 / fac;
     return e;
 }

 int main()
 {
     std::cout << std::setprecision(16)
               << "exp(1) = e¹ = " << std::exp(1) << '\\n'
               << "numbers::e  = " << std::numbers::e << '\\n'
               << "approx_e    = " << approx_e() << '\\n'
               << "FV of $100, continuously compounded at 3% for 1 year = "
               << std::setprecision(6) << 100 * std::exp(0.03) << '\\n';

     // special values
     std::cout << "exp(-0) = " << std::exp(-0.0) << '\\n'
               << "exp(-Inf) = " << std::exp(-INFINITY) << '\\n';

     // error handling
     errno = 0;
     std::feclearexcept(FE_ALL_EXCEPT);

     std::cout << "exp(710) = " << std::exp(710) << '\\n';

     if (errno == ERANGE)
         std::cout << "    errno == ERANGE: " << std::strerror(errno) << '\\n';
     if (std::fetestexcept(FE_OVERFLOW))
         std::cout << "    FE_OVERFLOW raised\\n";
 }

.SH Possible output:

 exp\fB(1)\fP = e¹ = 2.718281828459045
 numbers::e  = 2.718281828459045
 approx_e    = 2.718281828459045
 FV of $100, continuously compounded at 3% for 1 year = 103.045
 exp(-0) = 1
 exp(-Inf) = 0
 exp(710) = inf
     errno == ERANGE: Numerical result out of range
     FE_OVERFLOW raised

.SH See also

   exp2
   exp2f
   exp2l              returns 2 raised to the given power (\\({\\small 2^x}\\)2^x)
   \fI(C++11)\fP            \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   expm1
   expm1f             returns e raised to the given power, minus one (\\({\\small
   expm1l             e^x-1}\\)e^x-1)
   \fI(C++11)\fP            \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   log
   logf               computes natural (base e) logarithm (\\({\\small\\ln{x}}\\)ln(x))
   logl               \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   exp(std::complex)  complex base e exponential
                      \fI(function template)\fP
   exp(std::valarray) applies the function std::exp to each element of valarray
                      \fI(function template)\fP
   C documentation for
   exp
